1. Field of the Invention
The invention pertains to the field of recombinant deoxyribonucleic acid ("DNA") (or ribonucleic acid "RNA" in the case of a viral genome) host organisms for expressing recombinantly derived proteins. More particularly, the preferred recombinant nucleotides of the invention include a genetic insert coding for insect chitinase, which may be expressed in a variety of organisms. Particularly preferred forms of the invention include a recombinantly derived virus for accelerating the demise of insects, fungi, nematodes and other pests by causing them to express insect chitinase, and a highly insect-resistant recombinant plant that expresses insect chitinase.
2. Description of the Prior Art
Plants utilize chitinase in a variety of defensive mechanisms. By way of example, plant chitinase can degrade fungal cell walls as a defense against fungal pathogens. Additionally, plants secrete increased levels of chitinase in response to insect attack. Grains, in particular, often contain large amounts of chitinases. Unfortunately, while insects contain chitin in the midgut and exoskeleton, the plant chitinases seem to have very little influence upon the feeding activities of plant-eating insects, which have substantially overcome this avenue of plant defense.
Several plant, fungal, and yeast chitinase proteins and/or genes have been reported in the art, e.g., Cucumis sativa (Metraux et al., 1989), Saccharomyces cerevisiae (Kuranda and Robbins, 1989), Serratia marcescens A (Jones et al, 1986), Serratia marcescens B (Harpster and Dunsmuir, 1989), Streptomyces plicatus (Kuranda and Robbins, 1989), Streptomyces plicatus endo H (Robbins et al., 1984), Vibrio parahemolyticus (Kuranda and Robbins, 1989), Streptomyces erythraeus (Kamei et al., 1989), Bacillus circulans A1 (Watanabe et al., 1990), B. circulans D (Watanabe et al., 1992) and Arabidopsis thaliana (Samac et al., 1990).
The bean chitinase gene was recently inserted into transgenic tobacco (Nicotiana tabacum) seedlings, with the effect of producing tobacco plants that are resistant to the fungal pathogen Rhizoctonia solani, as reported by Broglie et al., 1991.